Growth of human tumor cells in macroporous microcarriers results in p53-independent, decreased cisplatin sensitivity relative to monolayers

Multicellular contact has been shown to influence the in vitro sensitivity of cells to drug treatment. We investigated the use of macroporous gelatin microcarriers, CultiSpher-G, as a convenient laboratory system for the mole cular analysis of this "contact effect". We determined that human A549 cell s can be grown in CultiSphers with growth and cell cycle parameters similar to those of monolayers. In addition, cells in CultiSphers express less p27 /kip1, an indicator of cell cycle arrest, than equivalent cells in monolaye rs. When treated with drugs, A549 cells grown in CultiSphers or monolayers accumulate equivalent amounts of platinum-DNA adducts and similar amounts o f doxorubicin. Moreover, A549 and KB-3-1 cells in CultiSphers have signific antly decreased sensitivity to cis-platinum(II)diammine dichloride (cisplat in), 4-hydroperoxycyclophosphamide, doxorubicin, and paclitaxel (taxol) com pared with cells in monolayers when assayed by clonogenic survival. Cisplat in treatment in monolayers or CultiSphers did not result in apoptotic cell death. In contrast, paclitaxel caused a significant amount of sub-G, DNA, a n indicator of apoptosis, which was diminished when cells were grown in Cul tiSphers compared with monolayers. When grown in CultiSphers, cells with ab rogated p53 function (A549/16E6 and NCl-H1299) were less sensitive to cispl atin than the corresponding monolayer cells, indicating that the decrease i n sensitivity is p53 independent. Taken together, the data suggest that Cul tiSpher-G microcarriers are a useful in vitro system to examine the effects of three-dimensional cell contact on drug sensitivity of human tumor cells .